U.S. patent publication No. US2002-0048137A1 discloses a capacitor foil for making a two-layered embedded capacitor including a conductive layer and a partially cured bonding layer having a relatively high dielectric constant. The high dielectric bonding layer is formed with epoxy or other polymer and is loaded with capacitive ceramic particles. The capacitor foil may be applied to a laminate having copper patterns thereon to define a PCB intermediate containing at least one buried capacitor, each of the copper patterns defines a ground plane, and the conductive layer constitutes a power plane for the capacitor.
U.S. Pat. No. 6,274,224 discloses a passive electrical article comprising (a) a first self-supporting substrate having two opposing major surfaces, (b) a second self-supporting substrate having two opposing major surfaces, and (c) an electrically insulating or electrically conducting layer comprising a polymer between the first and second substrate. One embodiment of the passive electrical article is an embedded capacitor formed by placing a layer of a high dielectric constant ceramic dispersed in an epoxy resin between two conductive electrode sheets, e.g., barium titanate in epoxy between copper foils. One of the epoxy resins used in this prior art is a blend of a diglycidylether of bisphenol A and a novolac epoxy. The blend of barium titanate particles and epoxy may be prepared by mixing together barium titanate, a ketone solution of epoxies, and a dispersing agent, preferably an anionic dispersant, for example, a copolymer of polyester and polyamine, commercially available from ICI Americas, Wilmington, Del., under the trade designation “Hypermeer PS3”. The insulating layer disclosed in this prior art can be improved in the aspects such as high dielectric property, high thermal resistance, a good bonding property.